Potentiostat/galvanostat with digital interface

ABSTRACT

A potentiostat/galvanostat employs a controller for providing digital control signals to a digital-to-analog converter (DAC) that generates an analog output signal in response to digital control signals. A high current driver produces a high current output in response to the analog output signal from the DAC. A high current monitor monitors the output from the high current driver to produce a feedback signal for the high current driver to control the current produced by the high current driver and to produce an output dependent on the current supplied from the high current driver for monitoring by the controller. A counter electrode contact for a counter electrode is connected with the output of the high current monitor. A working electrode contact for a working electrode is electrically connected with a fixed stable voltage potential to enable electrochemical analysis of material between the counter electrode and the working electrode. A low current driver produces a low current range output in response to an analog output signal from the DAC. A low current monitor monitors the working electrode contact to detect current at the working electrode contact to supply an output dependent on the current detected for monitoring by the controller and for providing a feedback signal to the low current driver in order to control the output of the low current driver to control current between the counter electrode contact and the working electrode contact.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/844,367 filed Sep. 3, 2015. The entire contents of thisapplication are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to an electrochemical instrumentfor electrochemical analysis and more particularly to apotentiostat/galvanostat.

BACKGROUND OF THE INVENTION

Potentiostats and galvanostats are commonly used in electrochemicalanalysis, electrosynthesis, sensing, production and related fields. Highaccuracy, low cost and multiple functions (e.g., cyclic and linear scanvoltammetry, various pulse voltammetric methods, AC voltammetry,electrochemical, impedance measurement, chronocoulometry, to name a fewfunctions) are desirable properties of potentiostats/galvanostats, forresearch, teaching, production, sensing and other applications. It wouldtherefore be desirable for an electrochemical instrument to have thecapability to provide both potentiostat and galvanostat functions with awide range of current as well as a practical digital interface to enablehigh speed performance.

SUMMARY OF THE INVENTION

In accordance with the present invention, an electrochemical instrumentis provided for conducting electrochemical analysis of materials. Theelectrochemical instrument may be in the form of apotentiostat/galvanostat for conducting electrochemical analysis ofmaterials positioned between a counter electrode and a working electrodeof the instrument. The electrochemical instrument may comprise acontroller, such as a microcontroller, for controlling operation of thecircuitry of the instrument. The controller may function to operatepursuant to a computer program as well as various inputs from a user toprovide various or selected parameters or modes of operation. Thecontroller produces desired digital control signals. A digital-to-analogconverter (DAC) may be provided in electrical communication with thecontroller for generating an analog output signal in response to digitalcontrol signals from the controller. A high current driver may beprovided in electrical communication with the DAC to produce a highcurrent range output in response to the analog output signal from theDAC. For example, the high current driver may produce a high currentrange output in the range of about a fraction of milliAmpere mA or a mAto about amperes As. As a specific optional example, the high currentdriver may produce current in the range of about 0.25 mA to about 2.5 A.A high current monitor may be provided in electrical communication withthe high current driver to monitor the high current range output fromthe high current driver. The high current monitor may produce a feedbacksignal for the high current driver in response to the current monitoredby the high current monitor to control the current produced by the highcurrent driver. The high current monitor may also supply an outputdependent on the current supplied from the high current driver formonitoring by the controller. The high current monitor may also supply aworking output signal at a working output for performing analysis of aselected material. For this purpose, a counter electrode contact may beprovided for electrical communication with the counter electrode andconnectable in electrical communication with the working output of thehigh current monitor. A working electrode contact may be provided forelectrical communication with a working electrode and may beelectrically connectable with a fixed stable voltage potential (forexample, ground or virtual ground) for enabling electrochemical analysisof material at or between the counter electrode and the workingelectrode. For example, a selected working output signal from the highcurrent monitor may be applied from the counter electrode at or throughthe material being analysed or tested and then to the working electrode.

A low current driver may also optionally be provided in electricalcommunication with the DAC to produce a low current range output inresponse to the analog output signal from the DAC. For example, a lowcurrent range output may be in the range of about nanoAmperes nAs, andperhaps even as small as picoAmperes pAs, to about a mA or a fraction ofa mA. As a specific optional example, the low current driver may producecurrent in the range of about 2.5 nA to 0.25 mA. The low current drivermay be in electrical communication with the counter electrode contact sothat the low current range output may be supplied by the low currentdriver to the counter electrode. A low current monitor may beconnectable in electrical communication with the working electrodecontact for detecting current at the working electrode contact. In a lowcurrent mode of operation, the low current range output from the lowcurrent driver may be supplied to the counter electrode through or atthe material being analysed or tested and then to the working electrode.The low current monitor in electrical communication with the workingelectrode may supply an output dependent on the current detected at theworking electrode contact for monitoring by the controller. The lowcurrent monitor may also provide a feedback signal for the low currentdriver in order to control the output of the low current driver tocontrol the current between the counter electrode contact and theworking electrode contact. The low current monitor may optionallyinclude a monitor amplifier having an amplifier input connectable inelectrical communication with the working electrode contact and havingan amplifier output. The low current monitor may also include an arrayof feedback resistors connected between the output of the monitoramplifier and the input of the monitor amplifier. The low currentmonitor may also include a monitor multiplexer, for example, an analogmultiplexer, in electrical communication with the controller forselecting at least one of the feedback resistors in the array forelectrical communication between the output and input of the monitoramplifier to control the output of the monitor amplifier.

The high current monitor may optionally include a first high currentrange monitoring circuit for monitoring current in a first high currentrange and a second high current monitoring circuit for monitoringcurrent in a second high current range. As an optional example, thefirst high current monitoring circuit may operate in a range of aboutmAs to about an A whereas the second high current monitoring circuit mayoperate in a range of about a fraction of a mA to about mAs. As a morespecific optional example, the high current monitoring circuit mayoperate in a range of about 25 mA to 2.5 A and the second high currentmonitoring circuit may operate in a range of about 0.25 mA to 25 mA. Ofcourse, the two ranges need not precisely overlap at a common end pointand such common end point can be altered to a different magnitude.

The instrument may also include a reference electrode contact forelectrical communication with a reference electrode for positioningrelative to the working electrode and counter electrode in communicationwith the material, and a buffer in electrical communication with thereference electrode contact for detecting voltage at the referenceelectrode contact. The buffer may supply an output dependent on thevoltage detected at the reference electrode contact that is bufferedfrom the reference electrode contact for monitoring by the controller.The buffer may also selectively provide a feedback signal for the highcurrent driver to control the output produced by the high current driverwhen operating in voltage mode at a high current or high power mode ofoperation in order to control the voltage at the reference electrodecontact. The buffer may also supply the feedback signal from the bufferto the low current driver to control the output produced by the lowcurrent driver to control the voltage at the reference electrode contactwhen operating in voltage mode at a low current or low power mode ofoperation. In order to accommodate such an optional arrangement havingboth a high current driver and a low current driver, the instrument mayalso include a high current switch for switchably connecting the highcurrent driver in and out of electrical communication with the counterelectrode contact and a low current switch for switchably connecting thelow current driver in and out of electrical communication with thecounter electrode contact. The controller may function to enable ordisable output from either or both of the high current or low currentdrivers to respectively provide a type of high current switch and a lowcurrent switch, respectively, to connect and disconnect from the counterelectrode contact. The controller may operate to control the highcurrent switch and the low current switch so that when the high currentswitch electrically connects the high current driver into electricalcommunication with the counter electrode contact, the controller causesthe low current switch to switch the lower current driver out ofelectrical communication with the counter electrode contact. Likewise,when the low current switch switches the low current driver intoelectrical communication with the counter electrode contact, the highcurrent switch electrically disconnects the high current driver fromelectrical communication with the counter electrode contact. For anoptional arrangement in which the high current monitor includes both afirst high current monitoring circuit and a second high currentmonitoring circuit, the high current switch may include a first highcurrent monitor switch for electrically connecting the first highcurrent range monitoring circuit in and out of electrical communicationwith the counter electrode contact and a second high current monitoringswitch for electrically connecting the second high current monitoringcircuit in and out of electrical communication with the counterelectrode contact. In operation, the controller may be in electricalcommunication with the first and second high current monitoring switchessuch that when one of the high current monitoring switches is turned onthe other high current monitoring switch is turned off and when at leastone of the high current monitoring switches is turned on then the lowcurrent switch is turned off under the control of the controller.

The instrument may also include a ground switch under the control of thecontroller for electrically connecting the working electrode contact inand out of electrical communication with a fixed stable voltagepotential such as ground or virtual ground. When the high current driveris switched by the high current switch to be in electrical communicationwith the counter electrode contact, such as when operating in a highpower or high current mode of operation, the controller may control theground switch to connect the working electrode contact to ground.

The instrument may also include a low current monitor switch under thecontrol of the controller for switchably connecting the workingelectrode contact in and out of electrical communication with the lowcurrent monitor. In a low power or low current mode of operation, thelow current monitor switch electrically connects the working electrodecontact into electrical communication with the low current monitor andthe low current switch operates to connect the low current driver inelectrical communication with the counter electrode contact. In a highcurrent or high power mode of operation, the low current monitor switchmay also function to disconnect the working electrode contact out ofelectrical communication with the low current monitor, and the lowcurrent switch may function to disconnect the low current driver out ofelectrical communication with the counter electrode contact.

Next, the instrument may also include a feedback multiplexer, forexample, an analog multiplexer, in electrical communication with thecontroller and in electrical communication with the high current monitorfor receiving the feedback signal from the high current monitor, thebuffer for receiving the feedback signal from the buffer, and the lowcurrent monitor for receiving the feedback signal from the low currentmonitor, and for switchably selecting which of the feedback signals, ora signal dependent thereon, is output by the feedback multiplexer underthe control of the controller. In this regard, the controller mayoperate to control the feedback multiplexer to supply the feedbacksignal from the high current monitor for the high current driver whenoperating in high current mode and to supply the feedback signal fromthe low current monitor for the low current driver when operating in lowcurrent mode, and to supply the feedback signal from the buffer for atleast one of the high current driver or low current driver whenoperating in voltage mode. For example, the feedback multiplexer maysupply the feedback signal from the buffer for the high current driverwhen operating in voltage mode at a high power mode of operation and forthe low current driver when operating in voltage mode at a low powermode of operation. Optionally, the first high current range monitoringcircuit may provide a first high current feedback signal for thefeedback multiplexer and the second high current monitoring circuit maysupply a second high current feedback signal for the feedbackmultiplexer. When operating in the high current mode, the multiplexerunder the control of the controller may selectively supply the firsthigh current feedback signal from the first high current rangemonitoring circuit for the high current driver when operating in firsthigh current range and selectively supply the second high currentfeedback signal from the second high current range monitoring circuitfor the high current driver when operating in the second high currentrange. The first high current range monitoring circuit may include afirst sense resistor connected in series between the high current driverand the counter electrode contact and a first differential amplifier,such as an instrumentation amplifier, connected across the first senseresistor to detect the voltage produced by the current flow through thefirst sense resistor to provide the first high current feedback signal.Likewise, the second high current range monitoring circuit may include asecond sense resistor connected in series between the high currentdriver and the counter electrode and a second differential amplifier,such as an instrumentation amplifier, connected across the second senseresistor to detect the voltage produced by current flow through thesecond sense resistor to provide the second high current feedbacksignal. Preferably, the first and second sense resistors are connectedin parallel circuits and have different magnitudes of resistance,optionally such as a 10² magnitude difference such as 0.1 and 10 ohmsfor example.

The instrument may also include an analog-to-digital converter (DAC) inelectrical communication with the outputs of the low current monitor,the buffer and the high current monitor to convert the output signals ofthe low current monitor, the buffer and the high current monitor todigital signals for the controller.

In an optional arrangement, the buffer may also be in electricalcommunication with the counter electrode contact for detecting a voltageat the counter electrode contact and for supplying a buffered outputindicating the voltage at the counter electrode contact for electricalcommunication with the controller.

High Current/High Power

In accordance with the present invention an electrochemical instrumentfor conducting an electrochemical analysis of selected materials may beconfigured, adjusted or set to operate in a high power or high currentmode of operation and as such may be in the configuration ofpotentiostat and/or galvanostat for providing selected electricalsignals to a material positioned between a counter electrode and aworking electrode. As configured for a high power or high current modeof operation, the electrochemical instrument may include a controllerfor providing digital control signals and a digital-to-analog converter(DAC) in electrical communication with the controller for generating ananalog output signal in response to digital control signals from thecontroller. A high current driver may be in electrical communicationwith the DAC to produce a high current range output in response to theanalog output signal from the DAC. For example, the high current rangeoutput may be in the ranges previously indicated. A high current monitormay be used in electrical communication with the high current driver tomonitor the current output by the high current driver. The high currentmonitor may produce a current feedback signal for the high currentdriver in response to the current monitored by the high current monitorto control the current produced by the high current driver. The highcurrent monitor may also supply an output dependent on the currentproduced by the high current driver for monitoring by the controller.The high current monitor may also supply a working output signal at awork output for application to a material, such as a material under testor analysis. For this purpose, a counter electrode contact forelectrical communication with a counter electrode is connectable inelectrical communication with the work output of the high currentmonitor. A working electrode contact for electrical communication with aworking electrode may be connected in electrical communication with afixed stable voltage potential, such as ground or virtual ground, forenabling electrochemical analysis of material at or between the counterelectrode and the working electrode. The high current monitor mayoptionally include a first high current range monitoring circuit formonitoring current in a first high current range and a second highcurrent monitoring circuit for monitoring current in a second highcurrent range. For example, the first and second high current ranges maybe in the ranges previously indicated. The high current monitor may alsoinclude a first high current monitor switch for electrically connectingthe first high current range monitoring circuit in and out of electricalcommunication with the counter electrode and a second high currentmonitoring switch for electrically connecting the second high currentmonitoring circuit in and out of electrical communication with thecounter electrode contact, optionally under the control of thecontroller which may be in electrical communication with the first andsecond high current monitoring switches.

The instrument may also include a reference electrode contact forelectrical communication with a reference electrode for positioningrelative to the working electrode and the counter electrode incommunication with the material. A buffer may be provided for electricalcommunication with the reference electrode contact for detecting voltageat the reference electrode contact and for supplying an output dependenton the voltage at the reference electrode contact that is buffered fromthe reference electrode contact for monitoring by the controller. Thebuffer may also provide a feedback signal for the high current driver tocontrol the output produced by the high current driver to control thevoltage at the reference electrode contact.

The instrument may also include a feedback multiplexer, optionally inthe form of an analog multiplexer, in electrical communication with thecontroller, and both in electrical communication with the high currentmonitor for receiving the feedback signal from the high current monitorand in electrical communication with the buffer for receiving thefeedback signal from the buffer for switchably selecting under thecontrol of the controller which of the feedback signals, or a signaldependent thereon, is output by the feedback multiplexer for the highcurrent driver. In current mode, the controller will switch the feedbackmultiplexer to output the feedback signal from the high current monitorfor feedback for the high current driver. In voltage mode, thecontroller will switch the feedback multiplexer to output the feedbacksignal from the buffer for feedback for the high current driver.Optionally, the first high current range monitoring circuit may providea first high current feedback signal for the feedback multiplexer andthe second high current range monitoring circuit may provide a secondhigh current feedback signal for the feedback multiplexer. The feedbackmultiplexer may operate under the control of the controller toselectively supply the first high current feedback signal, or a signaldependent thereon, from the first high current range monitoring circuitfor the high current driver when operating in the first high currentrange and to selectively supply the second high current feedback signal,or a signal dependent thereon, from the second high current rangemonitoring circuit for the high current driver when operating in thesecond high current range.

Optionally, the first high current range monitoring circuit may includea first sense resistor connected in series between the high currentdriver and the counter electrode contact, and a first differentialamplifier, such as an instrumentation amplifier, connected across thefirst sense resistor to detect the voltage generated by current flowthrough the first sense resistor to produce the first high currentfeedback signals and an output for monitoring by the controller.Likewise, the second high current range monitoring circuit mayoptionally include a second sense resistor connected in series betweenthe high current driver and the counter electrode contact, and a seconddifferential amplifier, such as an instrumentation amplifier, connectedacross the second sense resistor to detect the voltage generated by thecurrent flow through the second sense resistor to produce the secondhigh current feedback signal and an output for monitoring by thecontroller. Preferably, the first and second sense resistors areconnected in parallel circuits and have different magnitudes ofresistance, optionally such as a 10² magnitude difference such as 0.1and 10 ohms for example.

The instrument may also include an analog-to-digital converter (ADC) inelectrical communication with the controller and in electricalcommunication with the outputs of the buffer and the high currentmonitor to convert the output signals of the buffer and the high currentmonitor to a digital signal for the controller.

Optionally, the buffer may also be connectable in electricalcommunication with the counter electrode contact for detecting a voltageat the counter electrode contact for supplying a buffered outputrepresenting the voltage at the counter electrode contact for electricalcommunication with the controller.

Low Current/Low Power

In accordance with the present invention, the electromechanicalinstrument may be configured, adjusted, or set to operate, for example,as a potentiostat or a galvanostat in a low current or low power mode ofoperation. When so configured, the instrument includes a controller forproviding digital control signals, and a digital-to-analog converter(DAC) in electrical communication with the controller for generating ananalog output signal in response to digital control signals from thecontroller. A low current driver may be positioned in electricalcommunication with the DAC to produce a low current range output inresponse to the analog output signal from the DAC. For example, a lowcurrent range may be in the range previously indicated. A counterelectrode contact may be provided for electrical communication with acounter electrode and for electrical communication with the output ofthe low current driver. A working electrode contact may also be providedin electrical communication with a working electrode for enablingelectrochemical analysis of material between the counter electrode andthe working electrode. In operation, current from the low current drivermay be supplied to the counter electrode for application at or throughthe material to be analyzed or tested and then to the working electrode.

The instrument may also include a low current monitor connectable inelectrical communication with the working electrode contact fordetecting current at the working electrode contact and for supplying anoutput dependent on the current detected at the working electrodecontact for monitoring by the controller. The low current monitor mayalso provide a feedback signal for the low current driver in order tocontrol the output of the low current driver to control the currentbetween the counter electrode contact and the working electrode contact.The low current monitor may optionally include a monitor amplifier, suchas a current feedback amplifier or transimpedance amplifier, having aninput connectable in electrical communication with the working electrodecontact and providing an output. The low current monitor may alsoinclude an array of feedback resistors connected between the output ofthe monitor amplifier and the input of the monitor amplifier to providea feedback loop between the output and the input of the monitoramplifier. The low current monitor may also include a monitormultiplexer, for example, an analog multiplexer, in electricalcommunication with the controller for selecting at least one of thefeedback resistors in the array for electrical connection between theoutput and the input of the monitor amplifier to control the output ofthe monitor amplifier.

The instrument may optionally include a reference electrode contact forelectrical communication with a reference electrode for positioningrelative to the working electrode and the counter electrode incommunication with the material. The instrument may also include abuffer for electrical communication with the reference electrode contactfor detecting voltage at the reference electrode contact. The buffer mayfunction to supply an output dependent on the voltage at the referenceelectrode contact that is buffered from the reference electrode contactfor monitoring by the controller. The buffer may also provide a feedbacksignal for the low current driver to control the output produced by thelow current driver to control the voltage at the reference electrodecontact. In a voltage mode of operation, the voltage at the referenceelectrode contact may be monitored relative to voltage at the workingelectrode contact, which may, for example, be a virtual ground.

The instrument may also include a feedback multiplexer, for example, ananalog multiplexer, in electrical communication with the controller. Thefeedback multiplexer may also be in electrical communication with thebuffer for receiving the feedback signal from the buffer and inelectrical communication with the low current monitor for receiving thefeedback signal from the low current monitor for switchably selectingwhich of the feedback signals input to the feedback multiplexer, or asignal dependent thereon, will be output for the low current driverunder the control on the controller. In this regard, the controller mayfunction to control the feedback multiplexer to supply the feedbacksignal from the low current monitor for the low current driver whenoperating in low current mode and to selectively supply the feedbacksignal from the buffer for the low current driver when operating involtage mode.

The instrument may also include an analog-to-digital converter (ADC) inelectrical communication with the controller and in electricalcommunication with the outputs of the low current monitor and the bufferto convert the output of the low current monitor and the buffer to adigital signal for supply to the controller for monitoring by thecontroller.

Optionally, the buffer may also be connectable in electricalcommunication with the counter electrode contact for detecting a voltageat the counter electrode contact and for supplying a buffered outputrepresenting the voltage at the counter electrode contact for electricalcommunication with the controller.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the following detailed description ofexemplary embodiments of the present invention may be further understoodwhen read in conjunction with the appended drawings, wherein likeelements are numbered alike throughout, in which:

FIG. 1 schematically depicts a top-level block diagram of thepotentiostat/galvanostat circuitry;

FIG. 2 schematically depicts a block diagram of a high power or highcurrent circuit configuration for the potentiostat/galvanostat circuitryof FIG. 1;

FIG. 3 schematically depicts a block diagram of a low power or lowcurrent circuit configuration for the potentiostat/galvanostat circuitryof FIG. 1;

FIG. 4 is a circuit diagram of a microcontroller circuit used in thepotentiostat/galvanostat circuit of FIGS. 1-3 as shown in general by theMCU in FIGS. 1-3;

FIG. 5 is a circuit diagram of digital-to-analog circuitry (DAC)employing a DAC circuit and a conditioner circuit for thepotentiostat/galvanostat circuit as shown in general by the DAC in FIGS.1-3;

FIG. 6 is a circuit diagram of a feedback multiplexer circuit as shownin general by the MUX in FIGS. 1-3;

FIG. 7 is a circuit diagram of the setting control circuit shown ingeneral in FIGS. 1-3 and the high current driver shown in FIG. 1 and asmore specifically depicted as a high power op amp HP OPA in FIG. 2;

FIG. 8 is a circuit diagram of the high current monitor shown in FIG. 1and as shown more specifically shown by sense resistors Rs1 and Rs2 andinstrumentation amplifiers INA1 and INA2 in FIG. 2;

FIG. 9 is a circuit diagram of the low current driver and associatedswitch SW-5 as shown in FIG. 1 and as shown in more detail by the lowpower op amp LP OPA and switch SW-5 in FIG. 3;

FIG. 10 is a circuit diagram of the low current monitor shown in FIG. 1and as more specifically shown by the transimpedance amplifier TIA, the−10 gain amplifier and the monitor multiplexer MUX2 and associatedresistor array in FIG. 3;

FIG. 11 is a circuit diagram of the buffer circuitry Buffer and thecounter electrode contact CNT and the reference electrode contact REF asshown in FIGS. 1-3;

FIG. 12 is a circuit diagram of the working electrode contact WKG andthe associated switches SW-3 and SW-4 as shown in FIG. 1 and as shown ingreater detail by the working electrode contact WKG and switch SW-3 inFIG. 2 and by the working electrode contact WKG and switch SW-4 in FIG.3;

FIG. 13 is circuit diagram of an analog-to-digital converter circuitADC-LC and associated conditioner circuitry as incorporated in the ADCcircuitry shown in FIG. 1 and more specifically as the ADC-LC circuitand conditioner circuitry as shown in FIG. 3;

FIG. 14 is a circuit diagram of an analog-to-digital converter circuitADC-HC1 and associated conditioner circuit as depicted in FIG. 2 and asincorporated into the ADC circuit shown in FIG. 1;

FIG. 15 is a circuit diagram of an analog-to-digital converter circuitADC-HC2 and associated conditioner circuit as depicted in FIG. 2 and asincorporated into the ADC circuit shown in FIG. 1;

FIG. 16 is a circuit diagram of an analog-to-digital converter circuitADC-V and associated conditioner circuitry as shown in FIGS. 2 and 3 andas incorporated in the ADC circuit as shown in FIG. 1;

FIG. 17 is a circuit diagram of a reference voltage circuit forgenerating reference voltages of 1.25 volts 1 V25 and 2.5 volts 2 V50for the circuitry as shown in FIGS. 4-23;

FIG. 18 is a circuit diagram of an erasable programmable memory chip EP(EPROM) and associated circuitry for providing memory and program memoryfor the controller MCU as shown in FIGS. 1-4;

FIG. 19 is a circuit diagram of a communications port for the controllerMCU as shown in FIGS. 1-4;

FIG. 20 is a circuit diagram of a voltage filter circuit to provide afiltered supply voltage of +15 volts and −15 volts for the circuitry asshown in FIGS. 4-23;

FIG. 21 is a circuit diagram of power supply circuitry for providingoutputs of 5 volts and 3.3 volts for the circuitry as shown in FIGS.4-23;

FIG. 22 is a circuit diagram of fan circuitry for operating a fan forcooling the instrument having the circuitry generally shown in FIGS.1-23;

FIG. 23 is a circuit diagram of optional buffer circuitry asincorporated into the buffer of FIG. 1 to enable electricalcommunication and buffering between the counter electrode contact CNTand the controller MCU as shown in FIG. 1; and

FIG. 24 is a flow chart depicting operational program steps of theinstrument having the circuitry generally shown in FIGS. 1-3 and morespecifically shown in FIGS. 4-23.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the FIGS. and initially to FIG. 1, an electrochemicalinstrument, generally designated 30, is depicted for analyzing andtesting the electrochemical properties of a material disposed or placedin the receptacle 35 intermediate a counter electrode electricallyconnected with counter electrode contact CNT and a working electrodeelectrically connected at working electrode contact WKG so that adesired electrical signal may be applied to the material through thecounter and working electrode. In general, the instrument may functionto apply a selected current and/or voltage signal of a desiredmagnitude, wave form and duration to the material within the receptacle35 so that current flow from the counter electrode to the workingelectrode may be monitored. A reference electrode may be connected at areference electrode contact REF for positioning intermediate the counterelectrode and the working electrode at receptacle 35 to enable a voltagebetween the reference electrode and the working electrode to bemonitored. In operation the electrochemical instrument may function as apotentiostat by measuring and monitoring voltages between the referenceelectrode contact REF and the working electrode contact WKG or as agalvanostat by measuring and monitoring currents between the counterelectrode contact CNT and the working electrode contact WKG, or as acombined potentiostat/galvanostat whereby the instrument may be switchedbetween operation as a galvanostat and a potentiostat.

In general, the instrument 30 includes a high speed controller 40,preferably provided as a microcontroller MCU, to perform all control,setting and monitoring functions of the potentiostat/galvanostatcircuitry. Wide current range may be achieved, for example, from nAs(and perhaps pAs) to As, by coordination of different circuits. Highspeed high resolution analog-to-digital converters, ADC, 110 anddigital-to-analog converters, DAC, 50 are used to achieve high accuracyand high speed. A communications interface 45, such as one or more of aUART/RS232/USB interface, such as a serial interface, e.g., RS232, USB(“Universal Serial Bus”), a parallel interface such as GPIB, and/or awired or wireless interface such as a UART (universal asynchronousreceiver/transmitter) is available to communicate with external controldevices such as a computer (e.g., PC, Mac, Tablet), a network, a smartphone, or other selected device or system. Capability is also providedfor a multitude of electrochemical techniques, including but not limitedto, cyclic voltammetry (CV), linear scan voltammetry (LSV), variouspulse voltammetric techniques (differential pulse (DPV), normal pulse(NPV), differential normal pulse (DNPV), square wave (SWV),electrochemical impedance spectroscopy (EIS) and alternating currentvoltammetry (ACV). New features can be added, for example by user inputor software upgrading.

As a general overview, referring to FIG. 1, the instrument includes acontroller 40 preferably in the form of a microcontroller unit MCU thatfunctions to execute program instructions, respond to user inputs, andmonitor signals from the operational circuitry to produce digital outputsignals to control operation of the circuitry. Since the operationalcircuitry of the instrument 30 includes analog circuitry, the instrument30 includes a DAC, preferably high resolution and high speed, responsiveto digital signals from the MCU 40 to generate the required analogvoltage or current to drive high current driver 70 or the low currentdriver 80, as shown in FIG. 1. The instrument 30 also includes a ADC,preferably high speed and high resolution, for converting selectedanalog signal from the analog circuitry to digital signals for the MCU40. In a high current mode of operation, as provided by programinstructions and/or user input, the DAC drives the positive input of ahigh power op amp HP OPA 72 as shown in FIG. 2 whereas in a low currentmode of operation the DAC 50 drives the positive input of a low power opamp LP OPA 82 as shown in FIG. 3. The DAC output is controlled by theMCU and the output signal of the DAC 50 is bipolar which can be positiveor negative. When a high current mode is used, the low current LP OPAoutput is blocked by a high isolation analog relay SW-5, and one of twohigh current ranges are selected by activation of one of a pair ofanalog relays SW-1 and SW-2 under the control of the controller 40. Whena low current mode is used, the high current output is disabled by adisable pin of the high current OPA HP OPA 72 connected with the powerenable line PA EN from the controller 40. The output of the respectiveop amp, HP OPA 72 or LP OPA 82, supplies the working output for applyinga selected signal to the counter electrode contact CNT. A feedbacksignal dependent on the mode of operation selected (constant voltagemode or constant current mode, or high current or high power mode or lowcurrent or low power mode) is supplied to the negative input of therespective power op amp, HP OPA 72 or LP OPA 82, to form a negativefeedback amplifier circuit.

An analog feedback multiplexer MUX 100 is used to select constantvoltage mode or constant current mode under the control of thecontroller. In constant current mode, the feedback MUX 100 selects thefeedback signal automatically based on the current range. In constantvoltage mode, the feedback MUX 100 selects a voltage reference signal asthe feedback signal. For example, the MUX 100 may function to select aconstant voltage, a constant current in a high current range including,for example, a first range of high current and a second range of highcurrent, and a constant current in a low current range.

When operating in a low current mode of operation, the low current isautomatically selected by an array of precision resistors 136, as shownin FIG. 3, in a TIA circuit (a Transimpedance Amplifier Circuit)including the low current monitor circuit 130, as shown in FIG. 1, andas provided by the transimpedance amplifier TIA 132, the array offeedback resistors 136, the monitor multiplexer MUX2 134 and thenegative gain amplifier 138 shown in FIG. 3. The proper resistor of theresistor array 136 is selected by MUX2 134 which is controlled by outputfrom the MCU 40 to further select the appropriate low current.

Now, for a more detailed description of the general operation andconfiguration of the instrument circuitry, referring to the drawings,and initially to FIG. 1, the electrochemical instrument 30 includes acontroller unit 40 in the form of a microcontroller MCU which is used toperform all desired control, setting, monitoring and communicationfunctions for the unit. A communications interface 45 may beelectrically connected with the controller MCU to enable such controllerto communicate with external devices such as a computer (PC, MAC, orother type of computer device), network, smartphone or other types ofexternal devices. The communications interface 45 may include, forexample, one or more of a universal asynchronous receiver/transmitter(UART), a universal serial bus (USB) or other communication connectionsuch as a serial RS232 or parallel GPIB. The controller MCU 40 iselectrically connected with a digital-to-analog converter circuit DAC50, preferably high speed and high resolution, via an interface bus 55which may be in the form of a serial peripheral interface bus. Thecontroller MCU 40 provides digital control signals for the DAC 50 whichin turn generates an analog output signal on the output line VDAC inresponse to digital control signals from the controller, as shown inFIG. 1. The VDAC output signal from the DAC is supplied to settingcontrol circuitry 60 which functions to selectively output a signal to ahigh current driver 70 and a low current driver 80. The controller 40 isalso connected with the setting control circuit 60 by a power enableline PAEN which functions to enable the high current driver, whenoperating in high current mode, to produce the power output signal PAOUTin response to the VDAC output signal from the DAC and the powerenablement signal PAEN supplied to the setting control circuit 60. Whenthe high current driver is enabled to produce the power out signalPAOUT, switch SW-5 is opened under the control of the controller 40 todisconnect the low current driver 80. Alternatively, when the controller40 functions to produce a low current output from the low current driver80, when operating in low current mode, the power enablement line PAENis not enabled to prevent the high current driver from providing anoutput and switch SW-5 is closed to thereby connect the low currentdriver 80. The setting control circuit 60 supplies a signal to the lowcurrent driver 80 over the control line CTRL to drive the low currentdriver to produce an output. A high current monitor 90 is connected withthe output of the high current driver along the PAOUT line and functionsto monitor the current produced by the high current driver at PAOUT andto produce an output signal in response to the current being monitoredon the PAOUT line. Optionally, the high current monitor 90 may includeseparate monitoring circuits to monitor different current ranges of highcurrent such that a first monitoring circuit for monitoring current in afirst range of high current, for example, 25 mA to 2.5 A, is connectedvia switch SW-1 and a second monitoring circuit for monitoring currentin a second range of high current, e.g., 0.25 mA to 25 mA, is connectedvia switch SW-2. Switch SW-1 and switch SW-2 operate under the controlof the controller unit MCU 40 as shown in FIG. 1 so that a workingoutput current is supplied from the high current monitoring circuit 90selectively through switch SW-1 or SW-2, depending on the range ofcurrent, to the counter electrode contact CNT. The high current monitoralso supplies a high current feedback signal over the INA OUT line to afeedback multiplexer MUX 100 in a form of a digitally controlled analogmultiplexer 100. The high current monitor 90 also functions to supply anoutput signal on the INA OUT line to an analog-to-digital converter 110,preferably high speed and high resolution, which is connected with thecontroller 40 via interface bus 115, for example, in the form of aserial peripheral interface bus.

As shown in FIG. 1, switches SW-1 and SW-2 are connected from the outputof the high current monitor 90 to the counter electrode contact CNT forconnecting with a counter electrode for use at the receptacle 35. Theinstrument also includes a buffer circuit 120 that is connected with areference electrode contact REF that connects with a reference electrodepositioned at the receptacle 35. The reference electrode is typicallypositioned intermediate and spaced away from the counter electrodeconnected with counter electrode contact CNT and the working electrodeconnected with working electrode contact WKG at the receptacle 35. Thereference electrode contact REF is in electrical communication with thereference electrode which is positioned relative to the workingelectrode and the counter electrode at the receptacle in communicationwith a material placed in the receptacle for analysis. The bufferelectrically communicates with the reference electrode contact fordetecting voltage at the reference electrode contact. The bufferfunctions to supply an output REF OUT that is dependent on the voltagedetected at the reference electrode contact and that is buffered fromthe reference electrode contact for monitoring by the controller. Forthis purpose, the reference output line REF OUT is connected with theADC circuit 110. In addition, the buffer provides a feedback signal atthe REF OUT line to the feedback multiplexer 100 to control the outputproduced in a voltage mode of operation by either the high currentdriver 70 or the low current driver 60 depending on whether high currentor power or low current or power, respectively, is being utilized.Optionally, the buffer 120 may also be separately connected with thecounter electrode contact CNT to detect voltage at the counter electrodeand may function to supply a buffered output signal CNT OUT to anoptional analog-to-digital converter 125 that functions to convert theanalog signal from the buffer on the CNT OUT line to a digital signalfor supply to the controller MCU 40 to enable the controller to monitorthe voltage at the counter electrode contact CNT.

As shown in FIG. 1, the working electrode contact WKG may also beconnected to ground GND through switch SW-3 and connected with a lowcurrent monitor 130 through switch SW-4. When operating in high currentmode, the high current monitor is connected through either switch SW-1or switch SW-2, depending on the range of the high current, with thecounter electrode contact CNT, and the working electrode contact WKG isconnected to ground through switch SW-3 while switches SW-4 and SW-5 areopen under the control of the controller 40. When operating in lowcurrent mode, the low current driver 80 is connected to the counterelectrode contact CNT through switch SW-5 while switches SW-1 and SW-2are open and the power enable line PA EN to the setting controlcircuitry 60 is disabled to disconnect the high current driver from thecounter electrode contact CNT. Also in low current mode, the workingelectrode contact WKG is connected to the low current monitor 130 byclosing of switch SW-4 while switch SW-3 is open to disconnect theworking electrode contact WKG from ground under the control of thecontroller 40. When the working electrode contact WKG is connected viaswitch SW-4 to the low current monitor, a low current line TIA INconnects the low current monitor with the working electrode contact WKG.As such, the low current generated by the low current driver that passesthrough the material at the receptacle 35 from the counter electrode atcounter electrode contact CNT to the working electrode at workingelectrode contact WKG is monitored by the low current monitor 130. Thelow current supplied from the working electrode contact WKG on the TIAIN line is monitored by the low current monitor and an output signal TIAOUT is produced reflective of the current being monitored on the TIA INline. The TIA OUT line from the low current monitor 130 provides afeedback signal to the feedback multiplexer 100. The low current monitoralso supplies an output signal that is dependent on the input current atthe TIA IN to the analog-to-digital converter ADC 110 for monitoring bythe controller 40 over the interface bus 115. The low current monitor isunder the control of the controller by the MUX2 line that connects thecontroller with the low current monitor to enable the low currentmonitor to adjust to the current being detected at TIA IN line. Theanalog-to-digital converter ADC 110 functions to convert the analogsignals supplied on the TIA OUT line from the low current monitor 130,the REF OUT line from the buffer 120, and the INA OUT line from the highcurrent monitor 90 to digital signals for communication with thecontroller 40 over the interface bus 115. As such the instrument 30,under the control of the controller MCU, can operate in a first highcurrent mode by opening of switches SW-2, SW-4, and SW-5, and theclosing of switches SW-1, SW-3, or a second high current mode by openingof switches SW-1, SW-4, and SW-5, and the closing of switches SW-2 andSW-3, or in a voltage mode by the detection of the voltage at thereference electrode contact REF by the buffer circuit 120.

When operating in a high current mode, the controller MCU 40 can alsocontrol the feedback multiplexer 100 over the MUX line or bus so thatthe INA OUT signal supplied as an input to the MUX 100 is supplied atthe MUX OUT line to the high current driver 70 as a feedback signal tocontrol the output of the high current driver 70. When voltage mode isselected while the high current driver is in use the controller MCU 40can control the feedback multiplexer 100 over the MUX line or bus tosupply the REF OUT signal from the buffer 120 as a feedback signal tothe high current driver 70 over the MUX OUT line to control the voltageat the reference electrode. When the instrument is operated in a lowcurrent mode, the power enablement signal from the MCU 40 causes thesetting control circuit 60 to disable the high current driver 70 andswitch SW-5 is closed to connect the low current driver with the counterelectrode contact CNT. The controller 40 may also function to causeswitches SW-1 and SW-2 to open. The controller 40 also functions to openswitch SW-3 to disconnect to working electrode contact WKG from groundand to close switch SW-4 to connect the working electrode contact WKGwith the low current monitor 120 which functions to monitor the lowcurrent on the TIA in line. In response to the current input on the TIAin line, the low current monitor 120 produces a feedback signal on theTIA OUT line that is supplied to the feedback multiplexer 100 that iscontrolled by the controller MCU to supply the TIA OUT feedback signalfrom the low current monitor to the low current driver 80 over the MUXOUT line when operating in low current mode. When operating in voltagemode with the low current driver in use, the controller can control thefeedback multiplexer MUX 100 over the MUX OUT line or bus so that thefeedback signal from the buffer over the REF OUT line is supplied by thefeedback multiplexer 100 to the low current driver 80.

High Power/High Current

Referring to FIG. 2, the electrochemical instrument 30 is depicted ingreater detail for configuration for use in a high power mode providinga high current mode of operation and a voltage mode of operation. Asshown in FIG. 2, the controller MCU 40 functions to control theoperation of the circuitry and supplies a digital control signal overinterface bus 55 to a digital-to-analog converter circuit 50, as shownin FIG. 1, that includes the DAC circuit 52 connected with a conditionercircuit 54, as more specifically shown in FIG. 2. The DAC circuit 52functions to convert the digital signals from the controller MCU 40 intoanalog signals that are supplied to the conditioner circuit 54 whichfunctions to buffer and adjust the level of the signals to provide asuitable output to the setting control circuitry 60 to drive the highcurrent driver 70 shown in FIG. 1. When operating in the high powermode, the controller 40 enables the setting control circuitry 60 overthe power enable line PAEN to supply an output signal from theconditioner circuit 54 to the input of high power operational amp HP OPA70 which may function as a high current driver. The control circuitry 60is connected with the noninverting input or the +line of the HP OPA amp72. The output of the HP OPA amp 72 is supplied on the power output linePA OUT, as shown in FIG. 2, as an input to the high current monitor 90of FIG. 1 which as shown in FIG. 2 may include sense resistors RS1 andRS2, 91 and 92, respectively, and differential amplifiers INA1 93 andINA2 94. As shown in FIG. 2, the output of the high power amp HP OPA 72is connectable with the counter electrode control CNT by a parallelcircuit of the sense resistors 91 and 92. More specifically, the outputof the high power amp HP OPA 72 can be switchably connected through thefirst sense resistor RS1 91 by switch SW-1 to the counter electrodecontact CNT or alternatively through the second sense resistor RS2 92 byswitch SW-2 to the counter electrode contact CNT. A first differentialamplifier 93 is connected across the first sense resistor 91, whichpreferably is a high precision resistor, to detect the voltage generatedby the current flow through the first sense resistor 91 when switch SW-1is closed when the circuitry operates in a first range of high current.When the circuitry operates in a second range of high current, switchSW-1 is opened and SW-2 is closed so that current produced by the highpower amp HP OPA 72 flows through the second sense resistor 92 to thecounter electrode contact CNT. The current flow through the second senseresistor RS2 92 is detected by a second differential amplifier 94connected across the second sense resistor 92, which preferably is ahigh precision resistor, to detect the voltage generated by the currentflow through the second sense resistor 92. Accordingly, as shown in FIG.2, a first high current range monitoring circuit includes the firstsense resistor 91 and first differential amplifier 93 for monitoringcurrent in a first current range of high current. Likewise, a secondhigh current monitoring circuit includes the second sense resistor 92and the second differential amplifier 94 first for monitoring current ina second current range of high current. The first differential amplifier93 may be in the form of an instrumentation amplifier INA1 whereas thesecond differential amplifier 94 may be in the form of a secondinstrumentation amplifier INA2. In high current mode, the currentsensing resistor (RS1 or RS2) voltage drop is thereby sampled by a highaccuracy INA amplifier having a fixed gain to provide enough signalstrength to provide a feedback signal. As shown in FIG. 2, the firstdifferential amplifier 93 produces an output signal on the INA-1 OUTline connected at the output of the differential amplifier 93 for supplyto conditioner circuit 112 and then to the analog-to-digital converterADC circuit ADC-HC2 111 for electrical communication with the controllerMCU 40 so that the controller can monitor the output of the firstdifferential amplifier 93 to monitor the current flow through the firstsense resistor 91 when switch SW-1 is closed. The differential amplifier93 also supplies a feedback signal on the INA-1 OUT line to the feedbackmultiplexer MUX 100. Likewise, the second differential amplifier 94provides an output signal for supply through conditioner circuit 114 andADC circuit ADC-HC2 113 for electrical communication with the MCU 40 sothat the controller can monitor the output of the second differentialamplifier 94 to monitor the current flow through the second senseresistor 92 when switch SW-2 is closed. The differential amplifier 94also supplies a feedback signal on the INA-2 OUT line to the feedbackmultiplexer MUX 100.

As shown in FIG. 2, the working electrode contact WKG is connected toground GND by a closed switch SW-3 when the circuitry operates in thehigh power or high current mode. If the instrument 30 only operates in ahigh current mode, then switch SW-3 can be fixed in closed position oreven be replaced by hard wire to ground a shown in FIG. 2. As also shownin FIG. 2, buffer circuitry 120 connects with the reference electrodecontact REF to provide a buffered output signal on the REF OUT line tothe conditioner circuit 118 and then to ADC circuit ADC-V 117 forelectrical communication with the MCU 40 so that the controller 40 canmonitor the reference voltage at the reference electrode contact REF.The buffer 120 functions to buffer the voltage detected at the referenceelectrode contact REF from the circuitry connected with the output REFOUT line of the buffer. The REF OUT line of the buffer also supplies afeedback signal from the buffer to the feedback multiplexer MUX 100.

Under the control of the MCU 40 the feedback multiplexer 100, whenoperating in the high current or high power mode, selects which feedbacksignal from the INA-1 OUT line, the INA-2 OUT line or the REF OUT lineis switchably supplied as a negative feedback signal on the MUX OUT lineas a negative feedback signal to the inverting terminal (the—terminal)of the high power amp HP OPA 70. When operating in the first range ofhigh current such that switch SW-1 is closed and SW-2 is open, a firstrange of high current passing through the first sense resistor RS1 91 tothe counter electrode contact CNT is detected by the first differentialamplifier 93, and the MUX 100 is switched under the control of the MCU40 to supply the INA-1 OUT line signal reflective of the current flowthrough the first sense resistor RS1 91 at the MUX OUT line as anegative feedback signal at the inverting terminal of the high power ampHP OPA 72. When operating in voltage mode, at the first range of highcurrent when switch SW-1 is closed, the buffer 120 supplies a referencecontact voltage signal reflective of the voltage at the referenceelectrode contact REF as a feedback signal to the MUX 100 so that thecontroller MCU 40 can control the MUX 100 to switchably supply the REFOUT signal from the buffer 120 as a negative feedback signal at theinverting terminal of the high power amp HP OPA 72. When operating inthe second range of high current, switch SW-1 is open and switch SW-2 isclosed under the control of the controller 40. As a result, a secondrange of high current passing through the second sense resistor RS2 92to the counter electrode contact CNT is detected by the seconddifferential amplifier 94 which provides an output reflective of thecurrent flow through the second sense resistor RS2 92 on the INA-2 OUTline that is supplied to the MUX 100 as a feedback signal that can beswitchably supplied as a negative feedback on the MUX OUT line to theinverting terminal of the high power amp HP OPA 72. When operating involtage mode in the second range of high current, the feedback signalsupplied from the buffer 120 at the REF OUT line to the MUX 100 can beswitched at the MUX 100 under the control of the controller to besupplied as the negative output feedback signal to the invertingterminal of the high power amplifier HP OPA 72.

The output signal from the first differential amplifier 93 at the INA-1OUT line is also supplied to conditioner circuit 112 that functions tocondition the signal received at the INA-1 OUT line to an appropriatelevel for supply to the ADC circuit ADC-HC1 111 and may also function tobuffer the signal received on the INA-1 OUT line from the output to theADC converter circuit 111. The ADC circuit 111 functions to convert theanalog signals supplied from the conditioner circuitry 112 to a digitalsignal for the controller 40. Likewise, the output of the seconddifferential amplifier 94 is connected to a conditioner circuit 114 overthe INA-2 OUT line which functions to condition the analog signal to anappropriate level to supply to the ADC circuit 113 ADC-HC2 113 and mayalso function to buffer the signal supplied on the INA-2 OUT line fromthe signal supplied to the ADC circuit 113. The ADC circuit 113functions to convert the analog signals from the conditioner circuitry114 to a digital signal for the controller 40. The output of the buffersupplied on the REF OUT line is also supplied to a conditioner circuit118 that functions to adjust the level of the analog signal supplied onthe REF OUT line for supply to the ADC circuit ADC-V 17 which functionsto convert the analog signal supplied to the ADC-V 117 to theappropriate digital signal for supply to the controller MCU 40. Theconditioner circuit 118 may also function to buffer the input suppliedon the REF OUT line from the output to the ADC circuit ADC-V 117. Theanalog-to-digital converters, ADC-HC1 111, ADC-HC2 113, and ADC-V 117,are preferably high-speed and high accuracy converters that communicatewith the MCU 40 over interface bus 115. As such, the MCU 40 may functionto monitor the current flow through the first sense resistor 91 via theoutput of ADC-HC1 111, the current flow through the second senseresistor 92 via the output of ADC-HC2 113, and the voltage at thevoltage reference contact REF via the output of ADC-V 117.

Low Power/Low Current

Referring to FIG. 3, the electrochemical instrument 30 is depicted withcircuitry configured for use in a low power mode of operation providinga low current mode of operation and a voltage mode operation. As shownin FIG. 3, the controller MCU 40 provides digital control signals overinterface bus 55 to the DAC circuit 50 as shown in FIG. 1 which includesthe digital-to-analog converter circuit DAC 52 and associatedconditioner circuit 54, as shown in FIG. 3. The DAC circuit 52 functionsto convert the digital signal from the controller 40 to a suitableanalog signal that is supplied to conditioner circuit 54. Theconditioner circuit 54 functions to adjust the level of the analogoutput from the DAC 52, and to buffer the output of DAC 52, to asuitable level for supply to the setting control circuitry 60 which inturn supplies an output to the noninverting pin of a low power op amp LPOPA 82. The low power op amp circuit LP OPA 82 may function as a lowcurrent driver 80, as shown in FIG. 1. The output of the low power opamp LP OPA 82 is connected through switch SW-5 to the counter electrodecontact CNT. When operating in low current mode, switch SW-4 is closedto connect the working electrode contact WKG with the input of the lowcurrent monitoring circuitry 130 as shown in FIG. 1. If the instrument30 only operates in low power or low current mode switches SW-5 and SW-4may remain closed or may replaced with a hard wire connection. As shownin FIG. 3, the working electrode contact WKG is connected through switchSW-4, which is closed when operating in low current mode, so that thecurrent flow from the working electrode contact WKG is supplied to theinverting input of an amplifier 132 such as a current follower ortransimpedance amplifier TIA in form of an op amp TIA 132 having itsnoninverting terminal connected to ground GND. The output of thetransimpedance amplifier TIA 132 is connected through an array offeedback resistors 136 to a monitor multiplexer MUX2 134, in the form ofan analog multiplexer, that operates under the control of MCU 40, thatis in turn connected back to the inverting input of the transimpedanceamplifier TIA 132 to provide a feedback signal loop for the amplifierTIA 132. The monitor multiplexer 134 operates under the control of thecontroller to select the appropriate resistor in the resistor array 136having the appropriate resistance for the current being monitored in thelow current mode of operation for connection in the feedback loop.

The output of amp TIA 132 is supplied through a negative gain amplifier138 having a gain of negative 10, for example, to invert the output ofthe transimpedance amplifier TIA 132 and to amplify such signal to asuitable level for monitoring by MCU 40. The low current monitoringcircuit 130 shown in FIG. 1 includes the amp TIA 132, the negative gainamplifier 138, the monitor multiplexer MUX2 134, and the feedback arrayof resistors 136 shown in FIG. 3. The negative gain amplifier 138creates sufficient gain so that an output signal from the negative gainamplifier 138 is supplied at the PIA OUT line through a conditionercircuit 116 to an ADC circuit 119 for communication over the interfacebus 115 to the controller so that the controller can monitor the amountof current being detected and monitored at the TIA IN line. Theconditioner circuit 116 functions to condition the analog signal on theTIA OUT line to an appropriate level and to buffer such signal forsupply to the analog-to-digital converter ADC-LC 119 that functions toconvert the analog signal supplied by the conditioner circuit 116 to anappropriate digital signal for supply over the interface bus 115 to thecontroller 40. The output signal from the amplifier 138 at the TIA OUTline is also supplied as a feedback signal to the feedback multiplexerMUX 100.

As shown in FIG. 3, the buffer circuit 120 electrically connects withthe reference electrode contact REF to supply a buffered output signalat the REF OUT line reflective of the voltage detected at the referenceelectrode contact REF. In this regard, the buffer 120 supplies abuffered feedback signal reflective of the voltage detected at thereference electrode contact REF as in input to the feedback multiplexerMUX 100 on the REF OUT line. The buffer 120 also supplies an outputsignal on the REF OUT line reflective of the voltage detected at thereference electrode contact REF for supply to the MCU 40 throughconditioner circuit 118 and then through an ADC circuit ADC-V 117. Theconditioner circuit 118 functions to condition and buffer the analogsignal supplied from the REF OUT line to the appropriate level for theADC converter ADC-V so that the converter ADC-V functions to convert theanalog signal from the conditioner 118 to an appropriate digital outputfor supply to the controller 40 over bus 115 so that the level ofvoltage at the reference electrode contact REF can be monitored by thecontroller. The feedback multiplexer MUX 100 operates under the controlof the controller so that the feedback signal on the TIA OUT line can beswitchably supplied as a negative feedback at the inverting terminal ofthe low power amplifier LO OPA 82 when operating in low current mode.When operating in voltage mode, the controller MCU 40 can control thefeedback multiplexer MUX 100 to separately supply the feedback signal atthe REF OUT line from the buffer 120 reflective of the voltage detectedat the reference electrode contact REF as a negative feedback signal tothe inverting terminal of the low power amp LP OPA 82. In operation, theMCU 40 may function to monitor the current flow from the workingelectrode contact WKG via the output of ADC-LC 119 and the voltage atthe reference electrode contact REF via the output of ADC-V 117, withADC-V 117 and ADC-LC 119 preferably being high-speed and high-accuracyconverters that communicate with the controller MCU 40 over interfacebus 115.

Circuitry Components

Now, considering the operation of the circuitry in greater detail, thecontroller 40, with reference to FIG. 4, includes a microcontrollercircuit 41 in the form of controller chip ADuC7026_LQFP80. Themicrocontroller chip 41 functions to execute computer programs, receiveuser inputs, and monitor and control the operation of the circuitry forthe electrochemical instrument 30. As depicted in FIG. 4, themicrocontroller chip 41 has several of its pins connected directly orindirectly to a voltage source of approximately 3.3 volts. For example,pin 38 is connected to a 3.3 volt source through LED D21 thatilluminates to reflect operation of the instrument 30.

For purposes of generating proper supply voltage for the circuitry, afilter circuit, as shown in FIG. 20, is connected at jack J31 to apositive 15 volt source P15 V and to a negative 15 volt source N15 V atjack J33 each across a respective array of capacitors 151 and 152, thatare also connected to ground at jack J32 so that a filtered outputvoltage of +15 volts and −15 volts is generated as well as a groundconnection. The output of +15 volts is connected with an input of apower supply circuit 155 as shown in FIG. 21. As depicted a +15 voltsource is supplied to the input of a voltage regulator U1 157 providedas regulator chip LM7805, such that a 5 volt output is produced at theoutput of the regulator U1. The output of the voltage regulator U1 isalso supplied as an input to a low drop out regulator circuit LDO 158,provided by chip ADP3303, such that a +3.3 V output is produced at theoutput of the low drop out regulator chip LDO 158 as shown in FIG. 21.The 3.3 volt output from the low drop out regulator chip LDO may besupplied to circuit components as necessary including themicrocontroller chip 41 as shown in FIG. 4.

The microcontroller chip 41, as shown in FIG. 4, is also connected witha voltage reference of +2.5 V at 2 V50 at pin 78 as shown in FIG. 4. Inorder to produce selected voltage references, a voltage referencecircuit 154 is provided as shown in FIG. 17. As shown, a voltagereference chip VREF 156, as provided by chip LT460G, is connected withthe 5 volt input source from the power supply circuitry 155. The voltagereference chip VREF 156 is connected with a buffer BUFF 2 159, providedby chip AD822, to provide a first buffered voltage reference of 2.5volts 2 V50 and a second buffered reference voltage of 1.25 volts 1 V25.The 2.5 volt reference 2 V50 is connected with the microcontroller 41 atpin 78 as shown in FIG. 4.

As shown in FIG. 4, pins 18 and 19 of the microcontroller 41 areconnected with Jack J23 that can be used to illuminate a red and greenLED respectively. Pin 20 of the microcontroller 41 is connected with adownload Jack J21 that can be used to connect with a medium or device todownload information, instructions or programming, such as programupdates.

Referring to FIG. 18, computer memory 160 is provided in the form of anEEPROM (electrically erasable and programmable read only memory) chip EPand associated circuitry for storing selected programming instructionsand parameters for use by the microcontroller 41 shown in FIG. 4. Theforegoing instructions and parameters may be changed by reprogrammingthe memory. The EP chip communicates with the microcontroller 41 overline SCL which provides a clock line to pin 60 of the controller andline SDA which provides a data line, such as a serial data line, to pin59 of the microcontroller as shown in FIG. 4.

The microcontroller 41, as shown in FIG. 4, also includes a resetcircuit connected at pin 37 and Jack J22 to enable a reset of themicrocontroller 41. The microcontroller 41 also includes acommunications port, at pins 61 and 62 for example, to enable the chipto communicate with external devices such as computers, networks,smartphones and/or other selected media. For this purpose themicrocontroller 41 includes a port for connection with a transmissionline at TXmcu and a reception line at RXmcu connected respectively atpins 61 and 62 which in turn may connect with a communications jack 165such as a smart cable jack as shown in FIG. 19.

In order to remove heat from the instrument, the instrument 30 alsoincludes fan circuitry 180 to drive a fan as shown in FIG. 22. Briefly,a 15 volt input is supplied at a voltage regulator circuit U2, providedby chip LM7805, which is in turn supplies a 5 V output to a jack J36which connects with the fan.

The microcontroller 41 of FIG. 4 also communicates with adigital-to-analog converter DAC 50, as shown in FIG. 5, over interfacebus 55 as shown in FIG. 1. As more specifically shown in FIGS. 4 and 5,the microcontroller 41 communicates with the digital-to-analog circuitDAC 50 by an interface bus 55 that includes a master output/slave inputline MOSI connected between pin 52 of the microcontroller 41 and pin 6of a digital-to-analog converter chip DAC 52, as provided by chipAD5541_SOIC, as shown in FIG. 5, and by a slave-select line DAC_SSconnected between pin 51 of the microcontroller 41 and pin 4 of the DACchip, and by a serial clock line SCLK connected between pin 58 of themicrocontroller 41 and pin 5 of the DAC chip 52. As shown in FIG. 5, theDAC chip 52 is also connected to a reference voltage a 2.5 voltreference voltage 2 V50 at pin 3. The microcontroller 41 providesdigital signals to the DAC chip DAC 52 over the MOSI line and selectsthe DAC chip 52 for operation over the slave-select line DAC_SS. Timingclock signals are supplied over the clock line SCLK. As shown in FIGS. 2and 3, the DAC chip 52 in response to digital signals from themicrocontroller provides an analog output signal to input pin 3 of abuffer circuit BUFF3 54, provided by chip AD 822, which functions asconditioner circuitry 54 as shown in FIGS. 2 and 3 to provide a bufferedand conditioned analog output signal VDAC at the output pin 1 of thebuffer chip BUFF3 54 as shown in FIG. 5 at a suitable level for drivinga current or power driver.

The output VDAC from the conditioner circuit 54 is supplied as an inputto the setting control circuitry 60 as shown in FIG. 7. Morespecifically, the output VDAC from the conditioner circuitry 54 issupplied as an input at pin 3 of an op amp OPA1, as provided by chipAD822 and associated circuitry, as shown in FIG. 7, which functions asthe setting control circuitry 60 shown in FIGS. 1-3. The microcontroller41 is also in electrical communication with op the amp OPA1, as shown inFIG. 7, over power enable line PA_EN that functions to enable the highpower op amp HP OPA 72 (shown in FIG. 2), which may function as a highcurrent driver 70 (as shown in FIG. 1). The high power op amp HP OPA 72,shown in FIG. 2, includes the power amp chip PA, specifically providedas chip OPA548 and associated circuitry shown in FIG. 7, to provide ahigh power output on the output line PAout when the setting controlcircuit 60 produces an output control signal at the CTRL line from pin 1of OPA1 that is supplied to pin 1 of the PA 72 of the high power op ampHP OPA 72, as shown in FIGS. 2 and 7, and when the controller providesan enablement signal on the PA_EN line to the setting control circuit 60as shown in FIG. 7. As shown in FIGS. 4 and 7, the power enablement linePA_EN connects between pin 41 of the controller 41 as shown in FIG. 4and with pin 5 of setting control circuit OPA1 60 as shown in FIG. 7. Inorder to disable output from the high power amp 70, the controllerdisables the power enablement line PA_EN to thereby disable the outputPAout from the high power amp 72. As shown in FIG. 7, the settingcontrol circuit 60 also produces an output control signal at the CTRLline from pin 1 of OPA1 that is supplied to a low power op amp circuit82 (shown in FIG. 3) which functions as a low current driver 80 (shownin FIG. 1) as depicted in FIGS. 3 and 9.

The low current driver 80 (shown in FIG. 1) includes a low power op ampLP OP 82 (shown in FIG. 3) in the form of an op amp OPA3 as provided bychip AD822 and the associated circuitry as shown in FIG. 9. Now, withreference to FIG. 9, the control signal CTRL from the setting controlcircuit 60 is supplied as an input at pin 5 of op amp OPA3 82. Theoutput of op amp OPA3 82 at pin 7 is supplied as an input to a switchSW-5 that is provided by a digitally controlled analog relay RELAY5 asshown in FIG. 9. The microcontroller 41 communicates with the relayRELAY5, that operates as switch SW-5, over the relay line RLY5 that isconnected between pin 35 of the microcontroller 41 as shown in FIG. 4and pin 2 of the relay RELAY5 as shown in FIG. 9. The output of switchSW-5 is provided at pin 3 of the relay RELAY5 to produce an outputsignal that is supplied as a working signal in a low current or lowpower mode of operation to the counter electrode contact CNT for thecounter electrode at the receptacle 35 as shown in FIGS. 1 and 3.Accordingly, the microcontroller 41 may function to control switch SW-5so that when relay RELAY5 is activated the low power amp 82 is connectedwith the counter electrode contact CNT whereas when the controller opensrelay RELAY5 over the RLY5 line the low power amp LP OPA 82 isdisconnected from the counter electrode contact CNT.

As shown in FIG. 1, the output from the high current driver 70 issupplied on the PA OUT line to a high current monitor circuit 90 whenoperating in a high current or high power mode of operation. Referringto FIG. 8, the high current monitor circuitry, generally designated 90,is shown in greater detail along with switches SW-1 and SW-2. As shownin FIG. 8, the high power output signal PAout that is supplied from thehigh current driver 70 as a working signal is monitored by the highcurrent monitor 90 utilizing a first high current monitoring circuithaving a first sense resistor 91 and a first amplifier 93, such as adifferential amplifier, preferably in the form of an instrumentationamplifier INA1, as provided by chip INA121. The high current monitoringcircuit also includes a second high current monitoring circuit providedby a second sense resistor 92 and a second amplifier 94, such as adifferential amplifier, preferably provided by an instrumentationamplifier INA2, as provided specifically by chip INA121 as shown in FIG.8. As shown, the output on line PAout from the high power amp 72 issupplied through the first sense resistor RS1 91 and through the firstswitch SW-1 to the counter electrode contact CNT and is also supplied inparallel to the second sense resistor RS2 92 through the second switchSW-2 to the counter electrode contact CNT. The first and second senseresistors are selected to have different resistance so that the firsthigh current monitoring circuit utilizing sense resistor 91 may beemployed for a first range of current on line PAout from the high powerop amp HP OPA 72 and the second high current monitoring circuitemploying sense resistor 92 will be utilized for a second current rangeon line PAout from the high power op amp HP OPA 72. Switch SW-1 ispreferably provided by a digitally controlled analog relay RELAY1 thatoperates under the control of the microcontroller 41 over relay lineRLY1 between pin 30 of the microcontroller 41 as shown in FIG. 4 and pin2 of the relay circuit RELAY1 as shown in FIG. 8. Likewise, themicrocontroller 41 also controls the operation of switch SW-2 preferablyprovided by a digitally controlled analog relay RELAY2 shown in FIG. 8over a relay line RLY2 line that connects between pin 31 of themicrocontroller 41 a shown in FIG. 4 and pin 2 of the relay circuitRELAY2 as shown in FIG. 8.

For operation in a first range of high current, the high currentmonitoring circuitry 90 under the control of the microcontroller willoperate in such a manner whereby the microcontroller 41 will causeswitch SW-1 to close via the relay line RLY1 to connect the outputPAout, providing the working current from the high current driver, withthe counter electrode contact CNT via sense resistor 91 whereby suchcurrent flow is detected by the voltage across the first sense resistor91. When switch SW-1 is closed by the microcontroller 41, switch SW-2will be opened under the control of the microcontroller 41 via relayline RLY2. When switch SW-1 is closed the current flowing through thefirst sense resistor 91 will generate a voltage drop across the firstsense resistor 91 proportional to the current flow that will be detectedby the differential amplifier 93 that may be in the form of aninstrumentation amplifier as shown in FIG. 8. In response to the voltagedrop across the first sense resistor 91, the differential amp 93 willproduce an output INA1out dependent on the current flow through thefirst sense resistor 91 that will be supplied as an input to ananalog-to-digital converter circuit ADC 110, as shown in FIG. 1, formonitoring by the microcontroller 41. The output from the differentialamp 93 at INA1out can also be used as a feedback signal (of INA OUTshown in FIG. 1) for supply to the feedback multiplexer 100 MUX as shownin FIG. 2. Referring again to FIG. 8, when operating in a second highcurrent range the microcontroller 41 will cause switch SW-1 to open bysignals over relay line RLY1 and cause switch SW-2 to close by signalsover relay line RLY2 so that the second sense resistor 92, having adifferent resistance than the first sense resistor 91, connects theoutput of working current PAout from the high current driver with thecounter electrode contact CNT through the second switch SW-2. Whenswitch SW-2 is closed the current flow through the second sense resistor92 will generate a proportional or dependent voltage drop that can bemonitored by the differential amplifier 94 provided in the form of aninstrumentation amplifier INA2 to detect the voltage drop across thesecond sense resistor. In response to a voltage difference detectedacross the second sense resistor 92, the differential amplifier 94 willsupply an output signal INA2out dependent on the detected voltage, thatcan be used as a feedback signal (of INA OUT shown in FIG. 1) to thefeedback multiplexer MUX 100 as shown in FIGS. 1 and 2. In addition, theoutput INA2out supplied from the differential amplifier 94 can also besupplied as an input INA OUT to the ADC circuitry 110 as shown in FIG. 1for monitoring by the controller 40.

As shown generally in FIG. 2, the output INA-1 OUT from differentialamplifier 93 can be supplied for monitoring by the controller 40 throughconditioner circuitry 112 which functions to condition the level of theinput signal and buffer such input signal for supply to theanalog-to-digital converter circuit ADC-HC1 111. As more specificallyshown in FIG. 14, the output from the first monitoring circuitry of thehigh current monitor is supplied as output signal INA1out to the inputof a conditioner circuit 112 provided in the form of a buffer SFT-BUF-1,provided by chip AD822, and associated circuitry, that buffers andconditions the input signal INA1out to proper levels for supply to ananalog-to-digital converter 111 provided by ADC circuit chip ADC1,provided by chip LTC864A_SOIC, and associated circuitry, that functionsto convert the analog input from the conditioner circuit 112 to adigital output for supply to the microcontroller 41. The ADC circuitchip ADC1 is connected with the microcontroller 41 over an interface bus115, as shown in FIGS. 1 and 2, that includes a clock line SCLK, and amaster input/slave output line MISO and a control line ADC1_CNV thatrespectively connect with pins 58, 57, 56 of the microcontroller 41 asshown in FIG. 4.

As also generally shown in FIG. 2, the output INA-2 OUT fromdifferential amplifier 94 can be supplied for monitoring by thecontroller 40 through conditioner circuitry 114 which functions tocondition the level of the signal and buffer such signal for supply tothe analog-to-digital converter 113. As more specifically shown in FIG.15, the output from the second monitoring circuitry of the high currentmonitor is supplied as output signal INA2out to the input of aconditioner circuit 114 which includes a buffer SFT-BUF-2, provided aschip AD822, and associated circuitry, that buffers and conditions theinput signal INA2out to proper levels for supply to an analog-to-digitalconverter 113 provided by ADC chip ADC2, provided by chip LTC1864A_SOIC,and associated circuitry, that functions to convert the analog inputfrom the conditioner circuit 114 to a digital output for supply to themicrocontroller 41. The ADC circuit chip ADC2 is connected with themicrocontroller 41 over an interface bus 115 as shown in FIGS. 1 and 2.The interface bus 115 includes a clock line SCLK, a master input/slaveoutput line MISO and a control line ADC2_CNV that respectively connectwith pins 58, 57, and 55 of the microcontroller 41 as shown in FIG. 4.

The microcontroller 41 is also in electrical communication with thebuffer 120 to monitor the voltage at the reference electrode contact REFas generally shown in FIGS. 1, 2 and 3. As shown more specifically inFIG. 11, the buffer 120 includes a buffer chip BUF5, provided as chipAD822, and associated circuitry. The input at pin 3 of the buffer chipBUF5 is connected with the reference electrode contact REF at jack J62for the reference electrode so that the voltage appearing at thereference electrode contact will be supplied as an input at pin 3 to thebuffer chip BUF5. In response, the buffer chip BUF5 supplies an outputREFout at output pin 1 through resistor R65. The REFout line from thebuffer chip 5 provides a voltage reference feedback signal to thefeedback multiplexer MUX 100 as shown in FIGS. 1, 2 and 3 that isbuffered for the voltage input at pin 3 from the reference electrodecontact REF.

Referring again to FIG. 11, the buffer chip BUF5 connected with thereference electrode contact at jack J62 functions to detect the voltageor signal at the reference electrode contact REF and serves to provide abuffered output REFout at output pin 1 representing the voltage detectedat the reference electrode contact REF that can be monitored by themicrocontroller 41. For this purpose, the REFout from buffer chip BUF5is supplied to conditioner circuitry 118, as shown in FIG. 16, thatbuffers and conditions the signal to an appropriate level to supply toan ADC circuit 117 that converts the analog signal from the conditionercircuitry 118 to a suitable digital signal for supply to the controller40 over the interface bus 115. As shown more specifically in FIG. 16,the output REFout from the buffer 120, in the form of BUF5 as shown inFIG. 11, is supplied as an input at pin 3 of the buffer chip SFT-BUF-4,as provided by chip AD822, of the conditioner circuit 118. The bufferchip conditions the signal provided as an input at REFout to anappropriate level for input to the ADC circuit 117 provided by ADC chipADC4 in the form of chip LTC1864A_SOIC. The ADC chip ADC4 communicateswith the microcontroller 41 over an interface bus 115 having a clockline SCLK for clocking and timing of signals, a master input/slaveoutput MISO line for transmitting signals to the microcontroller 41 anda control line ADC4_CNV for receiving control signals from themicrocontroller 41, respectively connected with pins 58, 57 and 49 ofthe controller 41, as shown in FIG. 4.

Referring back again to FIG. 11, optionally, the buffer chip BUF5 ofbuffer 120 may also be connected with the counter electrode contact CNTat jack J61 for the counter electrode and selectively with the outputline CNT from the high current monitoring circuit 90 selectively throughthe first and second high current monitoring switches SW-1 and SW-2 asmore specifically shown in FIG. 8 or selectively with the output on theoutput line CNT from the low current driver through switch SW-5 as morespecifically shown in FIG. 9. Referring again to FIG. 11, the signal atthe counter electrode contact CNT provided by jack J61 is supplied as aninput to pin 5 of the buffer chip BUF5. In response, buffer chip BUF5supplies a buffered output CNTout at pin 7 that can be supplied to ADCcircuitry 125 as shown in FIG. 1 for monitoring by the microcontroller41 over the CNTmon line connected at pin 80 of the controller 41 asshown in FIG. 4. More specifically, with reference to FIG. 23, theCNTout signal from the buffer 120 representing the signal detected atthe counter electrode contact CNT can be supplied as an input to abuffer circuit 127 including buffer chip SFT-BUF-5, provided as chipAD822, and associated circuitry, to provide a buffered output CNTmon forsupply to the microcontroller 41 and preferably through ADC circuit 125as shown in FIG. 1.

As shown in FIG. 1, the working electrode contact WKG may be connectedto ground by switch SW-3 when the instrument is configured to operate inthe high power or high current mode or alternatively may be connected tothe low current monitor 130 by switch SW-4 when the instrument isconfigured to operate in the low power or low current mode. As shown ingreater detail in FIG. 12, the working electrode contact WKG provided atjack J63 is connected as an input to both switches SW-3 and SW-4 attheir respective input pin 4. As shown in FIG. 12, switch SW-3 isprovided in the form of a relay RELAY3, preferably a digitallycontrolled analog relay, that operates under the control of themicrocontroller over relay line RLY3 that is connected with pin 32 ofthe microcontroller 41 as shown in FIG. 4. Likewise, switch SW-4provided in the form of a relay RELAY4, preferably a digitallycontrolled analog replay, operates under the control of themicrocontroller 41 over relay line RLY4 that is connected with pin 33 ofthe microcontroller 41 as shown in FIG. 4. As such when operating in thehigh current or high power mode, the microcontroller 41 will cause relayRELAY3 to close thereby connecting the working electrode contact WKG atjack J63 with ground at output pin 3 of the relay RELAY3 and will causerelay RELAY4 to open to cause the working electrode contact WKG providedat jack J63 to be disconnected from the output of relay RELAY4 at theTIAin line at pin 3 of relay RELAY4. When operating in the low power orlow current mode, the controller 41 will cause relay RELAY3 to open todisconnect the working electrode contact WKG provided at jack J63 fromthe ground at output pin 3 and will cause relay RELAY4 to close toconnect the working electrode contact WKG with the output line TIAinwhich in turn connects to the low current monitoring circuitry 130 asshown in FIG. 1. As shown in FIG. 3, when switch SW-4 is closed the TIAin line that is output from switch SW-4 will be supplied as an input toan amplifier provided in the form of an op amp 132 configured as acurrent follower amplifier or a transimpedance amplifier TIA. The TIA INline is supplied through switch SW-4 to the inverting terminal of thetransimpedance amplifier TIA designated 132. The non-inverting input ofthe TIA amp 132 is connected to ground as shown in FIG. 3. The outputfrom the TIA amp 132 is supplied both as an input to an amplifier 138having a gain of negative 10 to invert the signal from the TIA amp forsupply as TIAout. In addition, the output from the TIA amp 132 is fedthrough an array of feedback resistors 136 through a monitor multiplexerMUX 134 under the control of the microcontroller 41 to provide afeedback signal to the inverting input of the TIA amp 132 to therebyprovide low current monitoring under the control of the controller 40.The low current monitoring circuitry, generally designated 130, isdepicted in greater detail in FIG. 10. With reference to FIG. 10, thesignal from the working electrode contact WKG is provided to themonitoring circuitry 130 on the TIAin line through switch SW-4, as showngenerally in FIG. 3, and is supplied to the inverting input pin 6 of anop amp circuit OPA2 133, provided by chip AD822, and the associatedcircuitry, as shown more specifically in FIG. 10. Op Amp OPA2 providesthe functionality of the transimpedance amplifier 132 at pins 5-8 andprovides the functionality of the negative gain amplifier 138 at pins1-4. As shown in FIG. 10, the TIAin signal is input at the invertinginput pin 6 of Op amp OPA2, while the noninverting input at pin 5 isconnected to ground. The TIA section of op amp OPA2 produces an outputat output pin 7 for supply to the resistor array 136, includingresistors RF1-RF8, as well as to the input at inverting pin 2 of thenegative gain amplifier section of op amp OPA2. The resistor array 136is connected between the output of the TIA amp 132 at output pin 7 ofthe TIA amplifier section of op amp OPA2 and the monitor multiplexerMUX2 134, such as a digitally controlled analog multiplexer, as providedby chip ADG1408, which functions to switchably connect a selectedresistor in the array under the control of the microcontroller 41 toproduce a switchably selected feedback signal that is supplied fromoutput pin 8 of the monitor multiplexer MUX2 to the inverting input atpin 6 of the TIA section of Op Amp OPA2. Considering this feedback loop,from pin 7 of Op amp OPA2, the output of the TIA amp 132 is fed to theresistor array 136 having separate resistors RF4, RF3, RF2, RF1, RF5,RF6, RF7, and RF8, of 10k, 1k, 100, 10, 100k, 1M, 10M, 50M,respectively, connected as inputs to the monitor multiplexer 134provided as MUX2. The output of the monitor multiplexer 134 is suppliedat pin 8 from MUX2 as a feedback input to pin 6 of the op amp OPA2. Themultiplexer chip MUX2 communicates with the microcontroller 41 over theMUX2 enablement line MUX2En so the microcontroller 41 can enable anddisable the monitor multiplexer MUX2 and over the MUX2 selection lines,Mux2Se10, Mux2Se11, Mux2Se12 lines, so that the microcontroller canswitchably select the appropriate resistor in the array 136 forconnection in the feedback loop while switchably disconnecting otherresistors. The Mux2En line is connected from pin 2 of monitormultiplexer Mux2 to pin 43 of the microcontroller 41 as shown in FIG. 4.Likewise, the Mux2Se10, Mux2Se11, Mux2Se12 lines shown in FIG. 10 are inturn connected with the microcontroller 41 at pins 46, 47 and 48,respectively. The microcontroller 41 functions to send a control signalto enable operation of the monitor MUX2 134 over the Mux2En line. Theparticular resistor that is selected for connection in the feedback loopis selected by the MUX selection signals sent by the micro processorover the Mux2Se10-2 lines. The particular resistor of the array 136 thatis selected is dependent on the current being monitored on the TIAoutline by the microcontroller 41 through conditioner circuit 116 and ADCcircuitry ADC-LC 119 as shown in FIG. 3. The TIAout line from the op AmpOPA2 133 also provides a feedback signal from the low current monitoringcircuitry to the feedback multiplexer circuitry MUX 100 as shown in FIG.3 and as shown more specifically in FIG. 6. Referring again back to FIG.10, the TIAout line from the Amp OPA2 133 is supplied to ADC circuitry100 as generally shown in FIG. 1 which includes the conditionercircuitry 116 and the ADC circuit ADC-LC 119 as shown in FIG. 3.

The conditioner circuitry 116 and the ADC circuitry ADC-LC 119 depictedin FIG. 3 is shown in greater detail in FIG. 13. Referring now to FIG.13, the conditioner circuitry 116 includes buffer circuitry SFT-BUF-3,as provided by chip AD822, and associated circuitry, which functions tocondition and level the analog signal input on the TIAout line to asuitable level for supply to an analog-to-digital converter circuitADC-LC 119 which is provided by ADC circuit ADC3 in the form of chipLTC1864A_SOIC. The output from the conditioner circuitry 116 at outputpin 7 of the buffer SFT-BUF-3 is supplied as an input to pin 2 of theADC ADC3 circuitry 119 as shown in FIG. 13. As such, the ADC circuitryADC3 functions to convert the analog signal being supplied to theconditioner circuitry 116 on the TIAout line at pin 3 of the SFT-BUF-3to a suitable digital signal for monitoring by the microcontroller 41.The ADC circuitry ADC3 119 as shown in FIG. 13 communicates with themicrocontroller 41 over an interface bus 115, as shown in FIG. 3,through lines SCLK which provides a clock signal from themicrocontroller, the master input/slave output line MISO that providessignals from the ADC circuitry at ADC3 to the microcontroller 41, andthe control line ADC3_CNV that provides for control signals from themicrocontroller 41 as shown in FIGS. 4 and 13. More specifically, asshown in FIGS. 4 and 13, the clock line SCLK connects pin 7 of the ADCcircuit ADC3, as shown in FIG. 13, with pin 58 of the microcontroller 41as shown in FIG. 4. The MISO line connects pin 6 of the ADC circuit ADC3as shown in FIG. 13 with the MISO pin 57 of the microcontroller 41 asshown in FIG. 4. Finally, the control line ADC3_CNV connects pin 5 ofthe ADC circuitry ADC3 as shown in FIG. 13 with pin 50 of themicrocontroller 41 as shown in FIG. 3. As such, as generally shown inFIG. 1, the TIA OUT line from the low current monitoring circuitry 130can be supplied through an ADC circuit 110 so that the analog outputfrom the low current monitor is converted to a suitable digital inputsignal for supply over the interface bus 115 to the MCU 40 to enable themicrocontroller to monitor the signal from the low current monitor.

As shown in FIG. 1, the MCU 40 is also connected with the feedbackmultiplexer MUX 100 over an interface bus MUX as shown in greater detailin FIG. 6. The feedback multiplexer 100 may include a multiplexer chipMUX1 in the form of chip ADG1408 and associated circuitry as shown inFIG. 6. The feedback multiplexer MUX1 and associated circuitry functionsto provide a digitally controlled analog multiplexer circuit which isconnected with the microcontroller 41 as shown in FIG. 4 over theinterface bus MUX as shown in FIG. 1. The interface bus MUX includes amultiplexer enablement line MUX1En that connects with pin 63 of themicrocontroller 41 shown in FIG. 4 and with pin 2 of the MUX1 circuit asshown in FIG. 6 to provide an enablement line so that the operation ofthe MUX1 circuit can be enabled by an enablement signal from themicrocontroller 41. The interface bus MUX as shown in FIG. 1 alsoincludes the output selection lines MUX1Se10, MUX1Se11, MUXSe12, thatconnect pins 64, 65 and 66, respectively, of the microcontroller 41 asshown in FIG. 4 with pins 1, 16 and 15 of the MUX1 circuit as shown inFIG. 6. The selection lines are utilized so that microcontroller 41 canselect which input provided by the feedback signals on the TIAout lineconnected to pin 4 of MUX1, the REFout line connected to pin 5 of MUX1,the INA2out line connected to pin 6 of MUX1 circuit, and the INA1outline connected to pin 7 of MUX1 may be switchably connected under thecontrol of the microcontroller 41 to provide an output from the MUX1circuit on the MUXout line connected at pin 8 of the MUX1 chip as shownin FIG. 6. As such, referring to FIG. 1, the MUX1 chip (shown in FIG. 6)of the feedback multiplexer 100 receives as inputs the feedback signalprovided on the TIAout line from the low current monitoring circuit 130,the voltage feedback signal provided on the REFout line from the buffer120 connected with the reference electrode contact REF, the feedbacksignal supplied on the INA OUT line including the feedback signal on theINA1out line (as shown in FIG. 2) and the feedback signal supplied onINA2out line (as shown in FIG. 2) for different ranges of currents fromthe high current monitoring circuitry 90. Accordingly, referring onceagain back to FIG. 6, the microcontroller 41 controls the operation ofthe feedback multiplexer MUX100 so that the input on the TIAout line issupplied on the MUXout line when operating in low current mode, theinput on the INA1out line is supplied on the MUXout line when operatingin a high current mode at a first selected range of current, the inputon the INA2out line is supplied on the MUXout line when operating inhigh current mode in a second selected range of current, and the inputon the REFout line is supplied on the MUXout line when operating involtage mode. As shown in FIG. 1, the MUXout line from the feedbackmultiplexer 100 is supplied as an input to the low current driver 80 andas input to the high current driver 70 so that a feedback signal maysupplied to the appropriate driver depending on the mode of operation.More specifically, the MUXout line from pin 8 of the feedbackmultiplexer MUX100, as shown in FIG. 6, is supplied as an output to theinverting input at pin 2 of the power amp OPA PA 72 as shown in FIG. 7so that when operating in the high current mode the MUXout signalsupplied to the power amp 72 shown in FIG. 7 may selectively be eitherthe feedback signal from line INA-1OUT (as shown in FIG. 2) whenoperating in the high current mode at a first selected range of currentor the feedback signal for line INA-2 OUT (as shown in FIG. 2) whenoperating in the high current mode at a second selected range ofcurrent, or alternatively the feedback signal on the REFOUT line whenoperating in the voltage mode in the high power or high currentoperation. The MUXout line, as shown in FIG. 6, is also supplied frompin 8 of MUX1 as an input as shown in FIG. 9 to pin 6 of the low currentamp OPA3 82. During operation in a low current or low power mode ofoperation, the feedback signal on the TIA OUT line (as shown in FIG. 3)from the low current monitor 130 can be supplied as a feedback signal onthe MUXout line to the low power amp 82 in low current mode oralternatively the feedback signal or the REFout line can be supplied onthe MUX out line to the low power amp 82 when operating in the voltagemode at the low power or low current level.

The electrochemical instrument 30 may operate under the control of acomputer executed program. An example of a selected program operation isdepicted in flow chart form in FIG. 24. Referring to FIG. 24, at startstep 200, the electrochemical instrument 30 is initially powered up, orafter being powered up is reset, to start operation. At step 205, thehardware and software of the instrument 30 is initialized and the outputfrom the instrument is temporarily disabled. At decision step 210, it isdetermined whether any new parameters or settings have been receivedsuch as current, timing, sequencing or other selected modes ofoperation. If new settings or parameters have been received, then atstep 215 the necessary settings are updated. If no new parameters orsettings are received at step 210, or once any such parameters orsettings have been updated in step 215, then at step 220 a decision ismade to determine whether a START command for starting operation hasbeen received. If not, the program moves back to step 210 to once againdetermine whether any new parameters or settings have been received. If,however, at decision step 220 it is determined that a START command hasbeen received, the program proceeds to step 225 to set the mode ofoperation of the instrument 30, such as voltage mode, high current modeor low current mode. At step 230, the instrument will then set therequired voltage or current for the selected mode of operation and thenat step 235 will set, calculate and control the timing of operation,such as the time for each data point, the total time of the measurement,or other selected timing parameters. Next, the instrument will performan auto range function at step 240 to detect and automatically selectthe proper current range by setting the circuitry to achieve the bestresult such as high resolution, low noise and high dynamic range, forexample. At step 245, the instrument will read the reference voltage andoutput current and then proceed to step 250 to check if there were anywarnings or alarms during the measurement. At step 255, the measuredresult, such as voltage and/or current, may be transmitted to anotherdevice such as a host computer or data collector via the communicationsport. Next, at step 260, the instrument will determine if there were anyhardware or software errors detected during the measurement. If so, theprogram will proceed to step 270 to disable the output. If no errorswere detected in step 260 the program will proceed to the decision step265 to determine whether a STOP command has been received. If a STOPcommand was been received, the program will again proceed to step 270 todisable the output. If a STOP command is not received at step 265, theprogram will proceed back to step 230 to again determine the setting ofthe voltage and current controls to again cycle through the steps fromstep 230 to step 265. Finally, at step 270, after the output has beendisabled, the program will then proceed back to step 210 to determinewhether any new parameters or settings have been received and thenproceed through the operational steps once again.

While certain embodiments of the present invention have been describedand/or exemplified above, various other embodiments will be apparent tothose skilled in the art from the foregoing disclosure. The presentinvention is, therefore, not limited to the particular embodimentsdescribed and/or exemplified, but is capable of considerable variationand modification without departure from the scope and spirit of theappended claims.

Moreover, as used herein, the term “about” means that dimensions, sizes,formulations, parameters, shapes and other quantities andcharacteristics are not and need not be exact, but may be approximateand/or larger or smaller, as desired, reflecting tolerances, conversionfactors, rounding off, measurement error and the like, and other factorsknown to those of skill in the art. In general, a dimension, size,formulation, parameter, shape or other quantity or characteristic is“about” or “approximate” whether or not expressly stated to be such. Itis noted that embodiments of very different sizes, shapes and dimensionsmay employ the described arrangements.

What is claimed is:
 1. An electrochemical instrument comprising: a. acontroller for providing digital control signals; b. a digital-to-analogconverter (DAC) in electrical communication with the controller forgenerating an analog output signal in response to digital controlsignals from the controller; c. a low current driver in electricalcommunication with the DAC to produce a low current range output inresponse to the analog output signal from the DAC; d. a counterelectrode contact for electrical communication with a counter electrodeconnectable in electrical communication with the output of the lowcurrent driver; e. a working electrode contact for electricalcommunication with a working electrode for enabling electrochemicalanalysis of material between the counter electrode and the workingelectrode; f. a low current monitor connectable in electricalcommunication with the working electrode contact for detecting currentat the working electrode contact and for supplying an output dependenton the current detected at the working electrode contact for monitoringby the controller and for providing a feedback signal for the lowcurrent driver in order to control the output of the low current driverto control the current between the counter electrode contact and theworking electrode contact, the low current monitor including i. amonitor amplifier having an input connectable in electricalcommunication with the working electrode contact and having an output,ii. an array of feedback resistors connected between the output of themonitor amplifier and input on the monitor amplifier, and iii. a monitoranalog multiplexer in electrical communication with the controller forselecting at least one of the feedback resistors in the array forelectrical connection between the output and input of the monitoramplifier to control the output of the monitor amplifier.
 2. Theinstrument of claim 1 including a reference electrode contact forelectrical communication with a reference electrode for positioningrelative to the working electrode and the counter electrode incommunication with the material, and a buffer for electricalcommunication with the reference electrode contact for detecting voltageat the reference electrode contact and for supplying an output dependenton the voltage at the reference electrode contact buffered from thereference electrode contact for monitoring by the controller and forproviding a feedback signal for the low current driver to control theoutput produced by the low current driver to control the voltage at thereference electrode contact.
 3. The instrument of claim 2 including afeedback analog multiplexer in electrical communication with thecontroller and in electrical communication with the buffer for receivingthe feedback signal from the buffer and the low current monitor forreceiving the feedback signal from the low current monitor and forswitchably selecting which of the feedback signals is output by thefeedback analog multiplexer for the low current driver under the controlof the controller.
 4. The instrument of claim 3 wherein the controllercontrols the feedback analog multiplexer to supply the feedback signalfrom the low current monitor to the low current driver when operating inlow current mode and to supply the feedback signal from the buffer tothe low current driver when operating in voltage mode.
 5. The instrumentof claim 4 wherein the monitor amplifier includes a transimpedanceamplifier having a gain dependent on the selection of a feedbackresistor in the array for electrical connection with the monitor analogmultiplexer.
 6. The instrument of claim 2 including an analog-to-digitalconverter (ADC) in electrical communication with the controller and inelectrical communication with the outputs of the low current monitor andthe buffer to convert the output signals of the low current monitor andthe buffer to a digital signal for supply to the controller.
 7. Anelectrochemical instrument comprising: a. a controller for producingdigital control signals; b. a digital-to-analog converter (DAC) inelectrical communication with the controller for generating an analogoutput signal in response to digital control signals from thecontroller; c. a high current driver in electrical communication withthe DAC to produce a high current range output in response to the analogoutput signal from the DAC; d. a high current monitor in electricalcommunication with the high current driver, the high current monitorproducing a feedback signal for the high current driver in response tothe current monitored by the high current monitor to control the currentproduced by the high current driver and for supplying an outputdependent on the current supplied from the high current driver; e. acounter electrode contact for electrical communication with a counterelectrode and connectable in electrical communication with the output ofthe high current monitor; f. a working electrode contact for electricalcommunication with a working electrode and electrically connectable witha fixed stable voltage potential for enabling electrochemical analysisof material between the counter electrode and the working electrode; g.a low current driver in electrical communication with the DAC to producea low current range output in response to the analog output signal fromthe DAC; and h. a low current monitor connectable in electricalcommunication with the working electrode contact for detecting currentat the working electrode contact and for supplying an output dependenton the current detected at the working electrode contact for monitoringby the controller and for providing a feedback signal for the lowcurrent driver in order to control the output of the low current driverto control the current between the counter electrode contact and theworking electrode contact, the low current monitor including i. amonitor amplifier having an input connectable in electricalcommunication with the working electrode contact and having an output,ii. an array of feedback resistors connected between the output of themonitor amplifier and input on the monitor amplifier, and iii. a monitoranalog multiplexer in electrical communication with the controller forselecting at least one of the feedback resistors in the array forelectrical communication between the output and input of the monitoramplifier to control the output of the monitor amplifier.
 8. Theinstrument of claim 7 wherein the high current monitor includes a firsthigh current range monitoring circuit for monitoring current in a firstcurrent range and a second high current monitoring circuit formonitoring current in a second current range.
 9. The instrument of claim7 including a reference electrode contact for electrical communicationwith a reference electrode for positioning relative to the workingelectrode and the counter electrode in communication with the materialand a buffer in electrical communication with the reference electrodecontact for detecting voltage at the reference electrode contact and forsupplying an output dependent on the voltage at the reference electrodecontact buffered from the reference electrode contact for monitoring bythe controller and for selectively providing a feedback signal for thehigh current driver to control the output produced by the high currentdriver to control the voltage at the reference electrode contact and forthe low current driver to control the output produced by the low currentdriver to control the voltage at the reference electrode contact. 10.The instrument of claim 9 including a high current switch for switchablyconnecting the high current driver in and out of electricalcommunication with the counter electrode contact and a low currentswitch for switchably connecting the low current driver in and out ofelectrical communication with the counter electrode contact, such thatthe controller controls the high current switch and the low currentswitch so that when the high current switch electrically connects thehigh current driver into electrical communication with the counterelectrode contact the controller causes the low current switch to switchthe low current driver out of electrical communication with the counterelectrode contact.
 11. The instrument of claim 10 wherein the highcurrent monitor includes a first high current range monitoring circuitfor monitoring current in a first current range and a second highcurrent monitoring circuit for monitoring current in a second currentrange and wherein the high current switch includes a first high currentmonitor switch for electrically connecting the first high current rangemonitoring circuit in and out of electrical communication with thecounter electrode contact and a second high current monitoring switchfor electrically connecting the second high current monitoring circuitin and out of electrical communication with the counter electrodecontact.
 12. The instrument of claim 11 wherein the controller is inelectrical communication with the first and second high currentmonitoring switches such that when one high current monitoring switch isturned on the other high current monitoring switch is turned off andwhen at least one of the high current monitoring switches is turned onthe low current switch is turned off under the control of thecontroller.
 13. The instrument of claim 10 including a ground switchunder the control of the controller for electrically connecting theworking electrode contact in and out of electrical communication withground when the high current driver is switched by the high currentswitch to be in electrical communication with the counter electrodecontact.
 14. The instrument of claim 10 including a low current monitorswitch under the control of the controller for switchably connecting theworking electrode contact in and out of electrical communication withthe low current monitor wherein the low current monitor switchelectrically connects the working electrode into electricalcommunication with the low current monitor when the low current switchoperates to connect the low current driver into electrical communicationwith the counter electrode contact.
 15. The instrument of claim 9including a feedback analog multiplexer in electrical communication withthe controller and in electrical communication with the high currentmonitor for receiving the feedback signal from the high current monitor,the buffer for receiving the feedback signal from the buffer, and thelow current monitor for receiving the feedback signal from the lowcurrent monitor, and for switchably selecting which of the feedbacksignals is output by the feedback analog multiplexer under the controlof the controller.
 16. The instrument of claim 15 wherein the controllercontrols the feedback analog multiplexer to supply the feedback signalfrom the high current monitor for the high current driver when operatingin high current mode and to supply the feedback signal from the lowcurrent monitor to the low current driver when operating in low currentmode and to supply the feedback signal from the buffer to at least oneof the high current driver or the low current driver when operating involtage mode.
 17. The instrument of claim 15 wherein the high currentmonitor includes a first high current range monitoring circuit formonitoring current in a first current range and a second high currentmonitoring circuit for monitoring current in a second current rangewherein the first high current range monitoring circuit provides a firsthigh current feedback signal for the feedback analog multiplexer and thesecond high current monitoring circuit supplies a second high currentfeedback signal for the feedback analog multiplexer, and when operatingin the high current mode the feedback analog multiplexer under controlof the controller selectively supplies the first high current feedbacksignal from the first high current range monitoring circuit for the highcurrent driver when operating in the first current range and selectivelysupplies the second high current feedback signal from the second highcurrent range monitoring circuit for the high current driver whenoperating in the second current range.
 18. The instrument of claim 17wherein the first high current range monitoring circuit includes a firstsense resistor connected in series between the high current driver andthe counter electrode contact and a first instrument amplifier connectedacross the first sense resistor to detect the voltage produced bycurrent flow through the first sense resistor to provide a first highcurrent feedback signal and wherein the second high current rangemonitoring circuit includes a second sense resistor connected in seriesbetween the high current driver and the counter electrode and a secondinstrument amplifier connected across the second sense resistor todetect the voltage produced by the current flow through the second senseresistor to provide a second high current feedback signal.
 19. Theinstrument of claim 9 including an analog-to-digital converter (ADC) inelectrical communication with the controller and in electricalcommunication with the outputs of the low current monitor, the bufferand the high current monitor to convert the output signals of the lowcurrent monitor, the buffer and the high current monitor to a digitalsignal for supply to the controller.